Concomitantly cross-linking and imparting stretch characteristics to a cellulosic fabric



United States Patent CONCOMITANTLY CROSS-LINKING AND IMPART- IN G STRETCH CHARACTERISTICS TO A 'CELLU- LOSIC FABRIC William G. Sloan, Metairie, Harry B. Moore, Harahan, and Albert S. Cooper, Jr., and Wilson A. Reeves, Metairie, La., assignors to the United States of America as represented by the Secretary of Agriculture N0 Drawing. Filed July 13, 1966, Ser. No. 564,734

Int. Cl. D06m 13/16 US. Cl. 8-120 3 Claims ABSTRACT OF THE DISCLOSURE Immersion of cellulosis fabric in a solution of an alkaline catalyzable cross-linking agent followed by immersion in an alkaline bath of mercerizing strength to concomitantly cross-link and impart stretch characteristics to the fabric.

A non-exclusive, irrevocable, royalty-free license in the invention herein described, for all government purposes, throughout the world, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to a continuous process for the production of cellulosic textile materials having excellent stretch-recovery and wet-wrinkle recovery properties. More specifically, it deals with a continuous process comprising shrinking cellulosic fibrous textile materials with an alkaline solution of mercerizing strength and subsequently reacting the alkali-treated cellulose (sodium cellulose) formed during the shrinking process with a suitable crosslinking agent which may be catalyzed by the alkaline agent.

According to this invention the sequence of application of the alkali of mercerizing strength and the crosslinking agent may be reversed. By the process, several steps which were necessary in prior-art methods are eliminated. Most important, no separate curing step is required.

The term cellulosic textile material or cellulosic fibrous materials, as used herein, relates to the natural cellulosic products such as cotton, linen, ramie, etc.; it also relates to the synthetic cellulosic fibers such as rayon, and the like. These products may be in the natural state, but better treatment is effected when the cellulosic material has been prepared by convertional procedures for removing natural waxes, and other noncellulosic impurities. The fibrous materials may be in the form of yarns; or they may be in the form of knit, or woven materials.

Processes for producing stretch cottons by slack mercerization or other alkali-contraction techniques are known in the art. Processes for the crosslinking, or chemical treatment of cotton using alkaline catalysts also .are known. However, in the present-day art of producing wrinkle-resistant cotton stretch fabrics, each of the two processes is carried out as a separate entity; this is frequently referred to as a two-stage process. That is, the fabric is first slack mercerized, then washed completely free of alkali, and dried. This is the first stage. The slackmercerized cellulosic material is then chemically treated by resination, or crosslinking, in the second-stage treatment. After resination, or crosslinking, the'fabrics are then dried, cured at a high temperature, washed to remove the excess crosslinking agent, catalyst, and unwanted byproducts, after which the fabrics are given a final drying. Frequently, the equipment for these two stages of treatment are at separate places in the plant, or the slackmercerized cellulosic material may be transported to another plant for the crosslinking treatment. In either case, since the chemical used for slack mercerization is 3,480,382 Patented Nov. 25, 1969 completely removed from the cellulosic material in the first stage, additional caustic solution must be used when an alkali-type catalyst is to be used in the second stage. US. Patent 3,145,132 teaches such a two-step batch finishing treatment in which complete removal of the agent (or reagent) that effects shrinkage of the cellulosic fibers is required, followed by drying before the crosslinking reactant can be applied to the cellulosic material.

It is an object of this invention to provide a process whereby cellulosic textile materials may be treated so as to produce stretch-recovery properties and a high level of wet-wrinkle resistance in a continuous sequence of finishing steps.

It is a further object of this invention to eliminate certain steps which are necessary in the above-mentioned two-stage batch process for producing wrinkle-resistant, cotton stretch fabrics, thereby providing added economy of time and expense.

These objects of our invention are accomplished by treating cellulosic yarns, woven or knit cellulosic fabrics by the following process which we have designated Process A.

(a) Impregnating the dry cellulosic material, without tension, with a 5 to 10 weight percent solution of at least one crosslinking reagent selected from the group consisting of dichloropropanol, epichlorohydrin, and the disodium salt of tri(sulfato-ethyl)sulfonium inner salt;

(b) Maintaining a period of dwell for about from 4 to 6 minutes at about from 65 to F.;

(c) Passing the wet cellulosic material through a pair of pair squeeze (padder) rolls to give a pickup of about from to weight percent;

((1) With minimum tension, pasing the wet material of step (c) into, and through a 30 to 35 weight percent aqueous solution of an alkaline swelling agent selected from the group consisting of sodium hydroxide, potassium hydroxide, and trimethyl benzyl ammonium hydroxide;

(e) Maintaining a period of dwell for about from 4 to 6 minutes to swell and shrink the cellulosic material;

(f) Removing the excess alkaline solution, as by mechanical means;

(g) Rinsing the wet material of step (f) in hot F.) water;

(h) Neutralizing any remaining alkali by rinsing in a weak acid solution;

(i) Rinsing to remove any residual acid, and thereafter (j) Drying with minimum tension the resulting cellulosic textile material characterized in that it has excellent stretch properties and improved wet-wrinkle resistance.

As will be described more fully below, this sequence of steps permits continuous processing of the fabric and also eliminates the steps of curing, washing, and drying which are normally carried out after crosslinking and drying. It also permits utilization of the alkali-swelling reagent of merceriz-ing strength as a catalyst during the crosslinking step. The economy of this reduction in processing steps is apparent.

It is also within the scope of our invention to treat the dry, woven or knit (knitted) fabric with an alkaline solution of mercerizing strength first. The excess alkaline solution is then removed by mechanical means and, thereafter, without washing or drying, the swollen cellulose is treated with the crosslinking agent. The treated fabric is then washed, neutralized with a weak acid solution, again rinsed, and dried. As noted above, no additonal curing step is required. This is Process B.

The sequence of steps described in both Process A and Process B of our invention permits continuous processing of the cellulosic material and also eliminates one washing step, two drying steps, and one curing step when compared with conventional processing. This is illustrated in the following table:

wet-wrinkle recovery. These properties imparted to cellulosic textile products provide greater comfort and con venience to the consumer and at the present time are in great demand by the public.

Processes of this Invention Alkaline swelling reagents which may be used in the fabric-contraction step include sodium hydroxide, potassium hydroxide, trimethyl benzyl ammonium hydroxide, and the like. Concentrations sufficient to bring about mercerization and attendant shrinkage of the cellulose are used. In general, concentrations ranging about from to 30 weight percent (OWS) at ambient room temperatures are required.

The fabric-contraction step is preferably carried out at a temperature of about from 65 to 85 F., and for a time sufficient to allow shrinkage to an extent which imparts stretchability to the fabric to occur. When applied to a dry fabric about from 0.5 to 5.0 minutes at ambient room temperatures is a good practice. However, when the crosslinking agent is applied first (Process A), the mercerizing solution should contain about from 30 to 35 weight percent (OWS) alkali and requires a longer period of dwell than when the alkaline solution is applied to a dry fabric. We have found that a period of dwell ranging about from four to six minutes caused good results to be obtained.

A crosslinking agent such as disodium salt of tris (sulfato-ethyDsulfonium. inner salt (called sulfonium salt below), dichloropropanol (DCP), epichlorohydrin, and the like, whose reaction with cellulose can be catalyzed by alkaline agents of mercerizing strength, is then applied. Application of the crosslinking agent to the fabric which has been wet with the alkaline solution may be by dipping, soaking, padding, spraying, brushing and the like, after which the excess solution may be removed by mechanical means such as a centrifuge, squeeze (padder) rolls, and the like. For continuous operation one or more pairs of squeeze (padder) rolls is a good practice. Concentrations of the crosslinking agent ranging about from five to ten weight percent (OWS) may be employed. When the pickup is properly adjusted, the treated fabric should also contain about from five to ten weight percent solid crosslinking agent (OWF).

When unscoured fabrics or yarns are used, addition of a small quantity of a wetting agent reduces the length of the period of dwell required to give a pickup of about from five to ten weight percent (OWF) of the crosslinking agent. Nonionic agents of the alkyl aryl polyether alcohol type are preferred.

After the reaction between the cellulose and the crosslinking reagent is completed, the fabric is thoroughly washed, soured, and again washed to remove all unusued reactant, catalyst, and/or byproducts. During all of the handling and final drying, it is essential that the fabric b processed with minimum tension to preserve the stretchability imparted by the shrinking or swelling treatment.

When treated by the process of this invention, cotton fabrics having improved strength-recovery properties and wet wrinkle-recovery properties are obtained. The values of these improved properties in a woven or knitted fabric are obvious to those skilled in the art of textile finishing. Furthermore, their value are indicated by the continuing increasing demands of the consumer for garments and other household items having both stretch properties and As noted above, the cellulosic materials may also be in the form of yarns. After swelling, shrinking and crosslinking, these yarns, which have excellent stretch-recovery properties and wet wrinkle-recovery properties may be knitted into garments or other types of apparel. As a result, desirable physical characteristics of these yarns are imparted to the product into which the yarn is fabricated.

The following examples are given to illustrate the in vention and in no Way are to be construed as restricting the obvious variations that may be used to achieve similar results. Temperatures are listed in Fahrenheit degrees, and the particular one employed is noted. Percentages are listed by weight on the weight of the solution (OWS), or by weight on the weight of the dry fabric (OWF). Solubility is qualitatively observed by treating fibers from the sample with 0.5 M concentrations of cupriethylene-diamine solution by the procedure descibed by Tripp et al., in Textile Research Journal 31, 295301 (1961). This procedure is a recognized test by those skilled in the art. Wet wrinkle-recovery angle is described in the American Dyest-uff Reporter, 52, (No. 11), 30 (1963). Growth is described in Example 4 of the instant application. Tear strength is determined according to ASTM designation: D142463.

Example 1 A portion of desized, scoured, and bleached x 80 cotton fabric was passed into, and through, a five weight percent solution of dichloropropanol (DCP), maintained at a period of dwell in the wet solution for about five minutes at 80 F., and then passed between pad rolls (squeezed) to give a pickup of about weight percent of the solution on the weight of the' dry fabric. Without drying, the squeezed fabric was passed into, and through, a 30 weight percent solution of sodium hydroxide at 80 F., with a period of dwell being maintained for about five minutes. The sodium hydroxide solution caused the fabric to shrink, thus producing a stretch-fabric while simultaneously causing the (DCP) to crosslink the cellulose. Then, with minimum tension the treated fabric was rinsed thoroughly in hot water, circa F neutralized in acetic acid, and dried at an air temperature of about 200 F.

Example 2 Using another portion of the 80 x 80 desized, scoured, and bleached cotton fabric of Example 1, the procedure of Example 1 was repeated except a 25 weight percent sodium hydroxide solution was applied first, maintained at a period of dwell for five minutes at 80 F., squeezed, and then treated with the five weight percent dichloropropanol solution. After a period of dwell of five minutes at 80 F., the treated fabric was rinsed in hot water, neutralized (soured) with acetic acid, and dried as in Example 1.

Example 3 Another portion of the 80 x 80 cotton fabric used in Example 1 was treated by the procedure of Example 1 except a 5% solution of the disodium salt of tris(sulfatoethyl)sulfonium inner salt was used instead of the 5% solution of (DCP).

Example 4 Another portion of the desized, scoured, and bleached 80 x 80 cotton fabric was treated as in Example 3 except that the fabric was first passed into a 25 weight percent solution of sodium hydroxide and, after the period of dwell, squeezed, and then passed into the five weight percent solution of the disodium salt of tris(sulfato-ethyl) sulfonium inner salt, again maintained at a period of dwell for five minutes at 80 F. After squeezlng to give about 100% pickup, the treated fabric was rinsed, soured, and dried.

It will be observed that the above treatments did not readded to the crosslinking agent both to give 0.1 weight percent (OWS). The results follow:

Growth after 10 cycles Control: to elongation EtOH-NaOH 5.3 Example 5 3.

It will be observed that the growth after crosslinking is reduced appreciably when compared with a control treated with ethyl alcohol which is not a crosslinking agent.

We claim:

1. A process for imparting excellent stretch-recovery and wet-wrinkle recovery properties to a woven cellulosic .textile material comprising quire a curing P- 15 (a) impregnating the dry cellulosic material, without Microscopic examination in cuprlcthylcnedlamme tension, with a five to 10 weight percent solut1on of (cuene) indicated that samples treated 1as 1:lescrbibed aboge at least one crosslinking reagent selectedflrfim the in Examples 3, and 4 were cross 111 cd, ccausc t c group consisting of dichloropropanol, epic oro ytreated samples did not dissolve after 30 minutes in the 90 drin, and the disodium salt f t i lf t th l) ul cueue. Control samples (which were treated with ethyl fo iu inner l alcohol first, thcn followed by Sodlum y (b) maintaining a period of dwell for about from four treated with sodium hydroxide first and followed by ethyl to i i t t b t f 65 to R; h alcohol) dissolv d readily i thc cllellc- (c) passing the wet cellulosic materia roug a pair The following table gives data showing that the four of squeeze (padder) rolls to give a pickup of about treated fabrics have better crease recovery, and less f 90 to 110 Weight percent; growth after repeated stretching to a fixed elongat1on. (d) i h i i t ion, passing the wet material Growth is a measure of dimensional stability and 15 deof Step into, d h h a to Weight fincd as thc PcYccl1t increase in the length of the Sample cent aqueous solution of an alkaline swelling reagent after being extended (stretched), and the load removed. 30 l d fr the group qonsisting 9f Sodlum The cycling test to measure growth was performed on an droxide, potassium hydroxide, and trimethyl benzyl Instron Tensile Tester on fabric samples ravelled to one iu hydroxide; inch, using a rate of extension of two inches per minute maintaining a period of dwell for about from four n a fiVc-inch gage lcngth- Tcst Spcclmcns Wcl'c cyclcd to six minutes to swell and shrlnk the cellulosic maten times from O to 15% elongation. The percent growth 35 t rial; was determined from the change in length of the fabric (f) removing the excess alkaline solution; strip after allowing it to recover for five minutes after the (g) rinsing the wet material of step (f) in hot (140 tenth cycle. F.) water;

Wet Filling Wrinkle Growth after Regovelrss Fi lll irgg 10 gyleleys I1 e e I 0 (W+ F), Strength, Elongatitihf N 0. Treatment, Example degrees grams percent Control: EtOH-NaOHU. 226 1, 033 4.3 D OH 236 1, 033 3.6 242 950 2.9 226 1,100 5.5 E CP 251 1,000 3.3 F Ex. 4. NaOH-Sulfonium Salt 236 850 3. 1

It Will be observed that:

(1) When the ethyl alcohol was applied to the control prior to the alkaline solution less filling growth resulted after ten cycles to 15% elongation than when these two steps were reversed (2) When the sodium hydroxide solution was applied to the cotton fabric prior to the application of the dichloropropanol, slightly better wrinkle recovery was obtained than when these two steps were reversed. However, no appreciable difference in the filling growth after ten cycles to 15% elongation resulted from this reversal of steps in the treating process (3) The treatment with the disodium salt of tris(sulfatoethyl)sulfonium inner salt resulted in less filling growth after ten cycles to 15% elongation, than the treatment with DCP. Again, there was no significant change in elongation when the steps were reversed.

Example 5 A five-gram skein of grey (unscoured) yarn is treated by the procedure of Example 1 except sufiicie'nt nonionic wetting agent of the alkyl aryl polyether alcohol type is 3. The process of claim 1 wherein the removal of excess alkaline solution in step (f) is accomplished by means of a pair of squeeze (padded) rolls.

References Cited UNITED STATES PATENTS 3,145,132 8/1964 Seltzer et al 8116 X GEORGE F. LESMES, Primary Examiner J. CANNON, Assistant Examiner U.S. Cl. X.R. 8-125 

